From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Investigation into the Wraith model's performance in relation to its body weight, comparing production and experimental cars.
| Identifier | ExFiles\Box 161a\3\ scan0004 | |
| Date | 6th January 1939 | |
| -3- WRAITH. BY.1/G.6.1.39. GEAR RATIO RELATIVE TO PERFORMANCE. (c) This subject at Sg{Arthur F. Sidgreaves - MD}'s request was completely reviewed in Mx.{John H Maddocks - Chief Proving Officer}12/N.24.2.38. and concurred in at a Conference 2.3.38. on the grounds that it was desirable in the interests of reliability, and performance was not noticeably debited by the change. PERFORMANCE IN RELATION TO BODY WEIGHTS. This matter has been raised by 'C' as a result of a complaint by Bennett. The investigation showed that the car in question weighed 42½ cwts. and from figures so far available at Derby it is established that bodies for Wraith that are being produced vary between 39 cwts. and 45½ cwts. indicating that some method of inspection is necessary at coachbuilders to keep the body weights within reasonable dimensions. Acceleration varies inversely as the weight of the car, and therefore a variation of 6½ cwts. as indicated represents 17% debit on performance. The average weight of all the Wraith experimental cars was 39½ cwts, the lightest being 38½, the heaviest is 40 cwts. 1 qr. The experimental weights included aluminium brake drums in certain cases, but if we add 42 lbs. which is the difference between the aluminium brake drum and the old cast iron one it still leaves a very serious debit against production bodies. The following summary outlines the position accurately up to the moment, and is included as a record :- Ref. Mx.{John H Maddocks - Chief Proving Officer}14/N.2.1.39. - Complaint WXA.27 Bennett. cwts. qrs. lbs. Average weight of complete Wraith cars. 42 2 0 " " Experimental Wraiths. 39 0 25 " " Last series - 25/30 39 3 0 Wraith chassis weighs 108 lbs. more than 25/30 chassis. The Wraith frame is stiffer, and should have led to reduced body weight. For comparison purposes if this 108 lbs. is added to the average weight of a complete 25/30 the total is 40. 2. 24. which shows the average Wraith body to be heavier by nearly 2 cwts. i.e. 1. 3. 4. | ||